Signal-receiving system



March 6, 1928. 1,661,261

P. B. MURPHY SIGNAL RECEIVING SYSTEM Filed Feb. 9. 1925 a; My

Patents?! Mar. 6, 1928.

UNITED STATES PATENT oFFicE.

more. .munrmr, or N'YAGK, new YORK, assrenoa, 3r MEBNE mmmm, re wEs'rERN anaemic comrm, 'mconrom'rzn, A coarom'non or new zonx.

SIGNAL-RECEIVE G SYBTEI.

Application filed February 9, 1925. Serial No. 7,745.

nals are composed by interrupting these cur-' rents at different rates toproduce different codes it is highly desirable that the receiving equipment shall respond quickly and function in a uniform manner in response to the signals even though the strength of such signals may vary due to various causes such as the attenuations caused by different lengths of transmission line over which the signals may be transmitted.

To attain this and other objects of the invention, there is rovided in accordance with one feature of t is invention means includ- 2 ing a space discharge device for roducing a uniform effect in a relay 'or in t e secondary of a transformer or an other similar type of apparatus from di erently attenuof said device.

Another feature of the invention is the arrangement of the input circuit and the output circuit of a space discharge device as to produce in the output circuit a uniform effect from difierently attenuated signals impressed on the input circuit. v

Another feature of the invention is the provision of means in the input-circuit of a space discharge device whereby a potential of electrons between the filament and the grid when the voltage of the incoming signals is increased above a certain value, is utilized to counteract the effect produced in the output circuit by the incoming signals and thereby ,to maintain the efiective output of the receiving circuit at' a constant value.

Another feature of the invention is the provision of means-in a space discharge device arranged for uniform' output for preventing self-oscillation although the output.

and input circuits are inductively coupled. This is done by an arrangement for actually short circuiting the output circuit to currents of the high frequency to which the inated signals impressed upon the input circuit set up in the input circuit, due to the flow put circuit is made responsive and also by short-circuiting the input circuit to currents of the low frequency to which the outputcircuit is made responsive.

Referring now to the drawings, Fig.1 6 illustrates one form of the invention as applied to a system in which high frequency alternating signals are transmitted over a line to cause the uniform operation. of a relay through a receiving circuit, involving a space discharge device employed as an amplifier and another space discharge device employed as a rectifier; while Fi 2 illustrates another form of the invention where. the rectifying space discharge device is employed to cause a uniform. effective output throu h a transformer, one winding of which is inc uded in the input circuit and another winding of which'is included in the output circuit of said device. Referring now specifically to Fi 7. 1, the

. transmission line 1 1s connected at t e trans mitting end to the transmitter 2 including a. source of hi h frequenc alternating current source 3 an a manual y operated key 4 in the primary circuit of a transformer 5, the secondary winding of which is included in the transmission line 1. It should be noted that several transmitters such as 2 having: sources of alternating 'current'of different high frequencies may be' connected to the transmissmn line 1 by meansv of tape, such as are shown at 6. At the receiving end of the transmissionline 1 a complete receiving circuit 10 is shown. This receiving circuit includes a transformer 11, a space discharge device 12 acting as an amplifier, another space discharge device '13 acting as a rectifier to the incoming signals, and a relay 14, the actions of which may be controlled by the amplified incoming signals'in a uniform manner in accordance with the princi les off this invention embodied in this circuit, as will be presently described.

Ta s' such as 15 from the transmission line 1 in icate that other receiving circuits, such as'10, may be connected to the line for the erent transmitter, that is, signals from the transmitter 2 may be received by the receiverlO, which is arranged to exclude signals from other transmitters, while a re-- no system as illustrated 3 to be induced in't e line 1 through the" transformer 5. Such sigials may, if the length of line is long, received at 10 greatly attenuated, while if the line is short theymay be received at 10 but slightly attenuated. It should be understood that the arran ement may be such that the stations provi ed with transmitters and receivers ma be located at varying distances from eac other. Hence, the transmission line over which the signals are transmitted and, therefore the attenuation of the signals may vary. Moreover, each. transmitter and lts corresponding receiver may be connected to different lines through suitable. switching arrangements such as manual plugs or jacks, or machine switching apparatus, and each of these lines may attenuate the transmitted signals differently.

In accordance with the invention, the means provided in connection with the re ceiving circuit 10 cause the greatly attenuated signals to produce the same effect in the receiver as signals less attenuated. That is, relay 14 is caused to act with practically the same magnetic pull regardless of the strength of the incoming signals. Hence, if this relay 14 has been once adjusted to respond properly to the weakest incoming slgnals likely to be received, it will also respond without any other adjustment 1n practically the same characteristic manner to incoming signals of greater strength such as will ordinarily be received over the shorter lines.

In order to make this action clear, it will at first be awumed that the incoming signals are greatly attenuated. The greatly attenuated high frequency alternating current signals will then be received through the transformer 11 and amplifier 12 in the usual manner well known in the art and be impressed through the condenser 17 and the input circuit of tube 13 on the grid 18. Because of the great attenuation in the signals, the ap lied alternating current voltage on the gr1d 18 will be of comparatively low magnitude. In fact, the magnitude of the positive half wave of the applled alternating current volta e will under these circumstances be less than the normally maintained negative grid potential. The grid 18 being maintained negative in respect to the filament 20 by the usual 0 battery 19, such incoming signals will therefore merely cause the grid 18 to become more or less negative and thus produce in the usual manner corresponding fluctuations of the current in the output circuit of tube 13. The output circuit of tube 13, which is connected through one winding of relay 14 and battery 22, is also connected through a condenser 23 to ground, and the resulting current in this circuit is thereby caused to be greatly stabilized. As is wel known, the interaction between the condenser 23 and the battery 22- may be made such that a practicall constant current will pass through the le t hand winding of relay 14 for each high frequency alternating current signal received over the line. Relay 14 will therefore normally be adjusted to respond to these signals and operate its current in the output circuit produced by this particular frequenc will determine the action of relay 14 prov1ded, of course, that the incoming signals are greatly attenuated.

It is essential that this relay 14 or any other similar signal responsive device should maintain these operating characteristics regardless of changes in intensit of the incoming signals and without a justment to compensate for varying attenuations. If, therefore, the relay is adjusted principally to operate properly in response to a certain pull on the armature when the current in the output circuit of the tube 13 is of minimum strength it should also in accordance with this invention exert practically the same pull when the current in the output circuit is of intermediate strength or of the maximum strength that may be obtained in practice when other transmission lines are used with this receiving CiI'Cllitk To this end, a branch of the input circuit is connected through the right hand winding of the relay 14 so that if a current is produced in this circuit it will pass through this winding in such a directlon that the magnetic flux caused thereby will counteract that produced in the left hand winding by the current in the output circuit. The magnitudes of these currents will always have a certain proportional relation to each other so that when the transmission line connected to the receiver is comparatively short and the attenuations of the incoming signals are correspondingly small, the resulting magnetic pull on the armature will be practically the same as when the line is long and the attenuations of the signals correspondingly greater. To produce such current in the input circuit from the less attenuated high frequency signals, it should be remembered that the a plied alternatin current volta e on the gri 18 must be suc as to make t e grid sitive in relation to 6 the filament 20, and t is will happen if the magnitude of the ositivd half wave of the'applied voltage is reater than the normal negative otentia of the grid. The grid will then ecome positive to an amount 10 equal to-the difference between the applied positive potential and the normal negative potential of the grid.

It is readily seen that if this is the case, a correspondlng current will flow between 1 the grid and the filament in a direction to oppose the battery 19. If it is assumed then that the applied alternating current voltage is greater than the norma ly maintained negative potential, the current flowing in the output circuit Will also assume a greater magnitude, and these two currents in the output and the input circuits will produce counteracting flux in the relay 14 so proportioned that the resulting magnetic pull on the armature will be approximately the same for any signals regardless of their magnitude As is well known in the art, oscillatory effects are generally produced when the output and input circuits are coupled together in space discharge devices of this type, and it now remains to be explained how such effects may be prevented in the tube 13. These effects may in accordance with this invention be avoided first by making the capacity-of the condenser 23 such that it will aliord a low impedance or act practically as a short circuit to the high frequency fluctuations in the output current, and therefore decrease the inductive efiect that may ordinarily be produced by such fluctuations in the input circuit through the windings of the relay 14; and secondly, by making the anti-resonant circuit 25 of such low impedance as to act as a practical short circuit to the low frequency that may be induced through the windings of relay 14 from the lower rate interrupt1ons in the output current, as produced by the incoming code signals. In this manner, therefore, any oscillatory effects that may ordinarily be set u between the input and output circuits /in thls device are entirely'eliminated.

r The modification of the invention shown in Fig. 2 diifers from the arrangement of- Fig. 1 only in that a three-winding transformer 30 is substituted for the relay 14 of the previous figure, the input circuit of the tube 13. being wired through one winding 31 of this transformer, the output cir cuit being wired through another winding 32 of the transformer, and a third winding 33 of the transformer being connected to an outgoing circuit. This arrangement operates in a manner similar to the arrangement described in connection with the 'previous figure to produce an effective uniform output from the tube 13 irrespective of ampli tug: variations in the input currents to the tu It should be understood that the invention is not limited to the particular arrangements of the output and input circuit shown in these two figures but that they merely serve as an illustration ofthe principles involved, and that any other devices similar to the relay 14 or transformer 30 may be employed in connection with the input and output circuits for obtaining a uniform effective output current. 1

What is claimed is:

.1. The method of equalizing the effects of alternating signaling currents of different strengths on a receiving device, which comprises transmitting current variations corresponding to the received signaling currents through branched paths having different volt-ampere characteristics, the characteristics of the paths being such that for weak incomin signaling currents the current output 0 one of said paths predomi- .wnat'es over the current output of the other path in a certain ratio and for stronger 1 received signaling currents said certain ra- "tion of the current outputs of the two paths is substantially maintained and opposing the outputs of said paths upon the receiving device.

2IA circuit for receiving alternating current signals of different strengths,-comprising two branched paths of different voltampere characteristics for transmitting current variations corresponding to the received alternating signaling currents, the characteristics of said paths being such that for weak incoming signaling currents the current output of one of said paths predominates over the current output of the other path in a certain ratio, and for stronger received signaling currents said certain ratio of the current outputs of the two paths is substantially maintained, a receiving device, and means for impressing the outputs of said two paths in opposition upon said receiving device.

3. A circuit for receiving alternating signaling currents of dilferent strengths, comprising two branch paths of diiferent voltampere characteristics for transmitting current variations corresponding to the received signaling currents, the characteristics of said paths being such that for Weak incoming currents the current output of one of said paths predominates over the current output of the other'of said paths by a given amountyand for stron outputs 0% the two paths also differ by substantially said given amount, said one path including the plate-filament circuit of a space discharge device, said other path iner incoming currents the current device, the other of said paths including the plate and filament of said space discharge, device, means for impressing the received alternating current signals on said paths in arallel, the characteristics of said paths eing such that for weak incoming signaling currents, the current output 01. sald one path is smaller than the current output of said other path in a certain ratio, and for stronger incoming signaling currents said certain ratio of the current'outputs of said paths is maintained and meaus to oppose the outputs of said paths comprising a relay having two inductively related windings one of said windings being in said one path and the other in said other path.

5. In a signaling system, the combination of means for transmitting high frequency alternating current signals over lines having different characteristics, whereby the signals received at the far ends of said l nes are differently attenuated, with a receiver for such attenuated signals comprising a space discharge device, an input and output circuit thereof, a relay having one wlnding in the input circuit and another winding in the output circuit, and means associated with said circuits for producing the same magnetic pull by said relay from any of said attenuated signals received regardless of their varying degree of attenuation.

6. In a. signaling system, a receiver for differently attenuated high frequency alternating current signals comprising a space discharge device, an input and an output circuit therefor, a relay having one winding in the input circuit and another winding in the output circuit of said device, and means associated with said circuits and said space discharge device for producing a certain electromagnetic pull by said relay when the received signal characteristics are such as to cause said relay to be influenced only by currents produced thlereby in the output circuit, and for producing substantially the same electromagnetic pull by said relay when the received signal characteristics are such as to cause said relay to be influenced by currents produced thereby in both the input and the output circuits.

7. In a signaling system, a combination of means for transmitting high frequency alternating current signals over lines having difierent characteristics, whereby said si' nals when received at the far ends of said lines are differently attenuated, with a receiver therefor com rising a space discharge device, an in ut and an output circuit therefor, a trans ormer having one winding in the input circuit and another winding in the output circuit of said device, and means associated with said circuits and the transformer'for producing substantially uniform alternating current signals fromany signals received regardless of the individual attenuations thereof. 8. In a signal receiving system, a space discharge device having its input circuit inductively coupled to its output circuit, and

means for substantially eliminating selfoscillatory effects in said device that may tend to be produced by said inductive coupling, said means including means in said input circuit and independent means in said output circuit.

9. In a signal receiving system, a space discharge device having its input and output circuits inductively coupled, a'nd means including a condenser to ground in the output circuit for substantially eliminating oscillatory effects from said device that may tend to be produced by said coupling.

10. In a signal receiving system, a space discharge device havingimput and out ut circuits inductively coupled so as to ten to produce self-oscillatory efiects, and means in said output circuit for substantially preventing such self-oscillatory effects from takingplace.

11. In a signaling system, means for receiving difi'erently attenuated alternating current signals comprising a space discharge device, an output and an input circuit therefor, a relay having one winding in the output circuit and another winding in the input circuit so arranged that said circuits are inductively coupled and so that currents produced in said circuits from any of said signals when received by said device will produce substantially the same electromagnetic pull by said relay, and means for eliminating self-oscillatory effects in said device that may tend to be produced by the inductive .coup ing of said circuits.

12. In a signaling system, a receiver for differently attenuated alternating current signals, comprising a space discharge device, an output circuit andv an input circuit therefor, ,a relay, means involving the inductive coupling of said output circuit and input circuit for producing a substantially uniform electromagnetic pull by said relay from any of said -diflerently attenuated signals when received by said device, and means including a condenser one side connected to ground and the other to the output circuit and an anti-resonant circuit included in said input circuit, for preventing self-oscillatory effects in said device, that may tend to be produced by the inductive coupling of said circuits.

13. In a signaling system, a receiver for differently attenuated high frequency alternating current signals comprising a space discharge device, an output and an input circuit inductively coupled together, and means effective through said coupling of the input and output circuits for producing substantially uniform high frequency alternating current signals from any of said received signals regardless of their attenuatiom'and means included in said input and output circuits for eliminating any -self-oscillatory effects in said device that may tend to be produced due to said inductively coupled circuits.

14. In a receiving circuit including a space discharge device having its input and output circuits so related to each other as to subject the device to regenerative effects when said device is subjected to differently cuits, said means comprisi attenuated current impulses, means for substantially eliminating such efiects comp'riss ing a mean s in the input circuit for preventing said input circuit from being responsive to frequencies to which the output circuit is responsive, and means for makm said. output circuit responsive. only to fque'ncies other than those to which the input circuit is responsive.

15. In a signaling system, a souroejof' coming waves consisting of a-hi h frequency wave modulated 'by a' wave 0 quency, a space discharge device arranged to function as a rectifier, said space device having in ut and-outputcircuits in ductivel couple ,to each other,-"said inpnt circuit eing supplied with said waves, and means to prevent self-oscillatory effects in said device due to the' indilgtive and output cir' coupling between the 7 input input circult for making said in ut circuit selectively responsive to the modulatedfre'. quency and means for making the ut' t lower are:

circuit responsive only to the modulating frequency. v

16. In a signaling system, a source of waves of varying energy level, a current regulating current-responsive receiving device therefor comprising a spac'e'dischar tube having a cathode, a grid and an 9.110 e, an inductance winding in. each of the circuits respectively connecting the cathode to the rid and the cathode to the anode, said win ings being magnetically interlinked, means for impressing said waves upon the circuit connecting said cathode to said grid, means in said circuits responsive to said waves for insurin that the resultant current flowing in one 0 said circuits through the inductance winding therein bears substantially the same relation to the current flowing in the other of said circuits through the inductance winding therein for all energy levels of said impressed waves andmeans responsive to the differential eiiects of current flow through said windings for produc-' -ing' a uniform effect.

17. In combination, a space discharge device having cathode, anode and impedance control elements, an input and an output circuit therefor, means to impress waves of varying amplitude on the input circuit of said device, an outgoing circuit, and means i for causing said waves of varying amplitude to produce substantially identical efiects in said outgoing circuit, comprising means for "coupling the input and output circuits of ,said device, means responsive to the imressed waves for roducing currents in the mput and output circuits, respectively, bear- ,ingat all times a definite, constant relation to each other and means differentially controlled-by sa1d currents in said input and "output circuits for controlling said outgoing "circuit.

witnesswhereof, I hereunto subscribe --11ny5name[this. 6th day of February A, D.,

1 PAUL 

